1. Field of Invention
The present invention relates to a calibration circuit and a calibration method for data recovery. More specifically, the present invention relates to a calibration circuit and a calibration method used in an optical storage system for data recovery.
2. Description of Related Art
Common optical storage systems include laser disks, such as compact disks (CDs) and digital versatile disks (DVDs). To reproduce data stored in an optical disk, an optical disc drive (ODD) projects a laser beam onto the surface of the optical disk. The ODD then reads the laser beam reflected from the optical disk. An electric signal generated according to the reflected laser beam is a radio frequency (RF) signal. There are many sources that may cause distortion on a RF signal, such as inter-symbol interference (ISI), electrical delay, scratches on the surface of the disks, aging of the disks, etc. Distortion leads to decrease in the quality of the RF signal and deterioration of recognition performance of the ODD.
Specifically, the ODD converts the reflected laser beam into an electric signal and then processes the electric signal to reproduce the originally stored binary data. In order to obtain reliable binary data, the ODD must accurately detect the phase and the level of the RF signal.
A conventional partial response maximum likelihood (PRML) technology is frequently used to recover the original data from the distorted data. Here, a partial response (PR) method is used to calibrate errors in signal levels to obtain digital data upon which data can be processed. To decode the digital data into the originally stored data, the Viterbi decoding mechanism of the maximum likelihood (ML) can be applied, and error calibration is performed on a bit-by-bit basis. Although the aforementioned PRML technology enhances the reliability of the RF signal, it also greatly complicates the system designs and hardware embodiments. Furthermore, the PMRL technology also consumes a lot of additional system resources.